Rustless iron manufacture



Patented May 14, 1940 UNITED STATES PATENT OFFICE RUSTLESS IRONMANUFACTURE Alexander L. Feild, Baltimore County, Md., as-

signor to Rustless Iron and Steel Corporation, Baltimore, Md., acorporation of Delaware 4 Claims.

This application is a division of my copending application 705,281 filedJanuary 4, 1934 which has matured into Patent No. 2,087,431 of July 20,1937, entitled Method of rolling rustless iron and product thereof, andthe invention relates to rustless iron manufactures and moreparticularly to highly heat-resistant manufactures of the classindicated.

Among the objects of my invention is the production of strong, ductileand readily workable products or manufactures, such as sheet, strip andbar stock, which are highly heat resistant and corrosion resistant underconditions of acid, alkali or salt atmospheres at high temperatures, andyet which lend themselves to convenient and economical working, as bymachining, punching, blanking, deep-drawing, spinning, upsetting orother known and commercially used forming operations, into variousultimate articles of manufactures, such as oil burner parts, roastingtrays, heat treatment boxes, airplane exhaust stacks, tubes for heatexchange apparatus, furnace parts and supports, fluid valves foroxidizing gases, as in blow torches and oxy-acetylene welding apparatus,and the like.

The invention accordingly consists in the features of construction,combination of elements and mixture of materials as described herein andthe scope of the application of which is indicated in the followingclaims.

As conducive to a clearer understanding of certain features of myinvention it may be noted at this point that rustless iron and steel insheet, strip and bar stock of low and intermediate chromium contents(12% to 17% Tare useful in the production of a wide variety ofhardenable articles, such as tools, cutlery and the like, as well as anumber of unhardenable products, such as decorative trim forarchitectural applications, automobile trim and similar uses wherecorrosion resistant characteristics are desired at room temperature, orat temperatures somewhat above this value, and under conditionsfostering corrosion. This class of manufactures, and the variousarticles made therefrom however, are neither designed nor adaptable forhigh temperature duty, especially high temperature duty under stronglyoxidizing or reducing conditions.

One of the outstanding objects of my invention is the efficient andeconomical production of heat resistant sheet, strip or bar stock, whichis strong, reasonably ductile and unhardenable by heat treatment, inconvenient sizes for handling and shipping to customer fabricators foruse in the ready fabrication of a variety of highly heat resistantarticles, a number of which are set forth above, peculiarly adapted towithstand the corrosive effects of furnace gases, sulphur fumes,moisture and like oxidizing or reducing agents at high temperatures.

Referring now more particularly to the practice of my invention, ingots,blooms or billets of rustless iron, produced for example as described inmy Patent No. 1,925,182 of September 5, 1933, entitled Process for themanufacture of rustless iron, and analyzing approximately 20% to 22%chromium, .05% to 20% carbon, with a permissible silicon content up toabout 2%, and the balance substantially iron, are hot rolled into sheetand strip. This hot-rolled sheet and strip is then annealed and pickledand then preferably cold rolled to sheet or strip of desired thickness.The sheet or strip is subsequently trimmed or slitted and made into aroll convenient for handling.

To achieve sheet, strip or bar stock of high tensile strength, goodimpact value. and fine surface texture, clean and free of surface scaleat a minimum of expense, the rolling operation is preferably carried outat room temperature using smooth, burnished, hardened and tempered alloysteel rolls. A total reduction of the sheet or strip bar stock of atleast about 50% in the cold rolling operation assures a high gradeproduct.

While the large percentages of chromium employed give the productdesired heat resistant characteristics, the workability of the materialis inclined to suffer The very low carbon contents employed, however,permit an increased workability of the metal in the presence of thesehigh percentages of chromium, achieving a manufacture of reasonably goodworking characteristics but one which is essentially unhardenable byheat treatment.

The sheet or strip is dense, tough, strong and shows a clean, brightsurface. This product or manufacture lends itself to a number of hot andcold working operations to achieve a wide variety of articles, parts andaccessories of exceptional heat resistant characteristics underoxidizing or reducing atmospheres at sustained or intermittent hightemperature conditions up to about 1050 C.

The rustless iron sheet or strip may be formed as by punching, blanking,deep-drawing, spinning, upsetting and the like and then welded eitherwith the electric arc or'the oxy-acetylene torch in accordance withknown welding practice, to form heat treating or carburizing boxes,calcining or roasting trays, tubes for heat exchangers oil cra hauststacks, oil parts The rstless iron bar stock may be readily cut, turned,drilled, threaded and otherwise machined to give a variety of articles,accessories and machine parts for high temperature uses, such as fluidvalves for oxidizing gases, furnace bars and supporting elements, needlevalves for blow torches and oxy-acetylene welding apparatus, orificesand valve seats for machinery or apparatus where high temperatureoxidizing and reducing conditions are encountered.

The workability of the heat resistant rustless iron sheet, strip or barstock, is appreciably improved by including in the metal a supplementaryaddition of manganese of from about 25% to 2%. Since the cost of makingthis supplementary addition is not particularly great, the improvedworking characteristics of the metal usually warrant such an addition.

Sheet, strip or bar stock of somewhat improved resistance to chlorideatmospheres under high temperature conditions is achieved bysupplementing the analysis set forth above with approximately .25% to 2%of molybdenum; furthermore, this supplementary element efiects a sounderand more dense metal of generally improved corrosion resistant and heatresistant characteristics. The use of a minimum of this material isdesired, however, since it is quite expensive and directly adds to thecost of the metal.

Supplementary additions of other ingredients, such as nickel and orcopper in amounts of about 25% to 2% contribute to certain of thephysical characteristics of the product or manufacture. Thesupplementary addition of nickel aids in the refinement of grainstructure, increases the toughness and tensile strength somewhat andlikewise increases the hardness of the metal. Copper acts in a waysimilar to the nickel addition, although to a lesser extent, and,furthermore, aids in certain forming operations of the sheet or strip,such as in the matter of deepdrawing.

While in the illustrative embodiment of my invention set forth aboveheat resistant sheet, strip or bar stock, unhardenable by heattreatment, containing, in addition to iron, chromium and carbon, isspecifically described, it will be understood that such a manufactureincluding one or more of the supplementary ingredients, silicon,manganese, molybdenum, nickel and copper, either singly or incombination, may be employed in accordance with the teachings of myinvention to achieve many highly beneficial results.

Thus it will be seen that there has been provided in this invention aproduct or manufacture o ..paratus, airplane exthe lilre.

in which the various objects hereinbeforc set forth, together with manythoroughly practical advantages, are successfully achieved. It will beseen that the highly heat resistant sheet, strip and bar stock, of highchromium content and low carbon content, which are unhardenable by heattreatment, readily lend themselves to economical and eificient workingor forming into a wide variety of heat resistant articles, accessoriesor apparatus parts adapted to withstand the many trying conditions ofactual high temperature use.

As many possible embodiments may be made of my invention and as manychanges may be made in the embodiment hereinbefore set forth, it'will beunderstood that all matter described herein is to be interpreted asillustrative, and not in a limiting sense.

I claim:

1. Tubes for use in oxidizing or reducing media under conditions ofintermittent heating, said tubes being heat-resistant and free fromhardening under such conditions, and comprising as essentialingredients, approximately, 20 per cent to 22 per cent chromium, .25 percent to 2 per cent manganese, .25 per cent to 2 per cent silicon, .05per cent to .20 per cent carbon, and the balance substantially iron.

2. Tubes for use in oxidizing or reducing media under conditions ofintermittent heating, said tubes being heat-resistant and free fromhardening under such conditions, and comprising as essentialingredients, approximately, 20 per cent to 22 per cent chromium, .25 percent to 2 per cent manganese, .25 per cent to 2 per cent silicon, .25per cent to 2 per cent molybdenum, .05 per cent to .20 per cent carbon,and the balance substantially iron.

3. Tubes for use in oxidizing or reducing media under conditions ofintermittent heating, said tubes being heat-resistant and free fromhardening under such conditions, and comprising as essentialingredients, approximately, 20 per cent to 22 per cent chromium, .25 percent to 2 per cent manganese, .25 per cent to 2 per cent silicon, .25per cent to 2 per cent copper, .05 per cent to .20 per cent carbon, andthe balance substantially iron.

4. Tubes for use in oxidizing or reducing media under conditions ofintermittent heating, said tubes being heat-resistant and free fromhardening under such conditions, and comprising as essentialingredients, approximately, 20 per cent to 22 per cent chromium, .25 percent to 2 per cent manganese, .25 per cent to 2 per cent silicon, .25per cent to 2 per cent molybdenum, .25 per cent to 2 percent copper, .05per cent to .20 per cent carbon, and the balance substantially iron.

ALEXANDER L. FEILD.

